Uveitis is a disease of the eye which can be located throughout the eye including the posterior and anterior chambers of the eye as well as the vitreous body. Uveitis, the inflammation of the uvea, is responsible for about 10% of the visual impairment in the United States.
Panuveitis refers to inflammation of the entire uveal (vascular) layer of the eye. Posterior uveitis generally refers to chorioretinitis and anterior uveitis refers to iridocyclitis. The inflammatory products, that is, cells, fibrin, excess protein, of these inflammations are commonly found in the fluid spaces of the eye including the anterior chamber, posterior chamber and vitreous space as well as the tissue involved in the inflammatory response. Uveitis may occur following surgical or traumatic injury to the eye, as a component of an autoimmune disorder such as rheumatoid arthritis, Behcet's disease, ankylosing spondylitis, sarcoidosis, as an isolated immune mediated ocular disorder, i.e., pars planitis, iridodyclitis etc., unassociated with known etiologies, and following certain systemic diseases which cause antibody-antigen complexes to be deposited in uveal tissues. Together these disorders represent non-infectious uveitities.
Cyclosporine A, a 1.2 kd cyclic peptide which is essentially insoluble in water effectively inhibits the development of experimentally induced uveitis. In human trials, cyclosporine A has been shown to be effective in treating chronic uveitis, especially that associated with Behcet's disease.
Unfortunately, systemic therapy with cyclosporine A has serious drawbacks. Cyclosporine A used systemically has also been associated with a high incidence of renal toxicity, some cases of hepatotoxicity, hypertension, and an increased incidence of opportunistic infections. The systemic side effects of cyclosporine A are so severe and so common that its use to treat life-threatening or in some cases severe sight-threatening disease is not recommended. The systemic toxicity is such that the National Eye Institute has recommended that, for uveitis inflicting one eye, cyclosporine should not be administered. Finally, a systemic application of cyclosporine A is limited by its prohibitive cost. Also, it should be noted that because of poor ocular availability, topical delivery does not result in the obtention of therapeutic levels of the drug in the back of the eye.
Accordingly, there exists a strong need for the elimination of the undesirable physiological and economic problems associated with cyclosporine A treatment of uveitis, while maintaining the advantageous therapeutic properties of this treatment.
The systemic toxicity of cyclosporine A may be minimized by delivering the drug locally. Although direct intravitreal injection prevents experimental autoimmune uveitis (EAU) , repeated injection is not a practical mode of administration.
Due to the risks that certain drugs impose, researchers have developed systems for administering such drugs to aid in the treatment of ailments and diseases. The systems have been designed largely to reduce and to control the release rate of incorporated drugs. However, these systems fail to achieve the surprising and unexpected results obtained by the present invention.
For example, U.S. Pat. No. 5,091,185 to Castillo et al. relates to implantable pellets for veterinary use comprising a bioactive material such as somatotropin coated with a polyvinyl alcohol polymer to prolong the release of the bioactive material after implantation. Parenteral administration of the coated pellet is by subcutaneous implantation and may be accomplished surgically or by injecting small pellets through a needle. However, the Castillo patent does not teach that the polyvinyl alcohol polymer should be heated to temperatures greater than about 100.degree. C. to induce changes in the crystal structure of the polymer to render it nonerodible. Somatotropins are heat sensitive and rapidly decompose on heating above 100.degree. C. so such heating would be impractical for the systems described in the Castillo patent.
U.S. Pat No. 4,300,557 to Refojo et al. relates to an improved process for dispensing a lipid-soluble, labile drug by diffusion from an implantable silicon capsule to a site within an animal body being treated with the drug, wherein the silicon capsule is provided with a tube sealed at its distal end and through the interior wall of which is cut a longitudinal slit of 1 to 1.5 mm for filling the capsule following implantation. The capsule is surgically implanted near the site being treated so that the tube is accessible for filling without further surgical procedures. In another aspect of the invention, a drug is dispensed at a constant rate through an expandable, silicon microballoon implanted periocularly to an intraocular site within an animal body.
U.S. Pat No. 4,649,047 to Kaswan relates to a method for the treatment of, for example, uveitis occurring throughout the globe of the eye, by topical administration of cyclosporine to the eye.
U.S. Pat No. 4,923,699 to Kaufman discloses an eye treatment system wherein three dimensional particles of bioerodible material of a specific size which are suspended in a liquid carrier or ointment carrier having a pH acceptable to the eye are delivered topically to the eye. Various agents may be added to increase viscosity, promote suspension and/or improve ocular compatibility.
U.S. Pat No. 3,832,252 to Higuchi et al. relates to a drug delivery device comprising an inner solid matrix with solid particles of drug dispersed therethrough. Any solid material chemically compatible with the drug and permeable to passage of the drug by diffusion can be employed.
U.S. Pat No. 4,309,996 to Theeuwes relates to a system comprising a microporous diffuser for delivering a beneficial agent to a fluid environment of use at a zero order rate for an increased length of time at that rate. The system consists essentially of a microporous wall, or a part microporous part semi-permeable wall, surrounding a compartment having a space containing the agent separated by a partition from a space containing an expandable entity.
U.S. Pat No. 4,309,776 to Berguer relates to an intravascular implantation device having a chamber for containing transplanted cells that is implanted in a wall of a blood vessel or to be implanted between an artery and a vein in a wall of each for the purpose of introducing hormonal components into the bloodstream of a human being. It is disclosed that the material of which the chamber-forming device is made must be tolerated in a blood vessel without causing thrombosis and should permit the choice of various degrees of porosity.
U.S. Pat No. 4,973,304 to Graham et al. relates to devices which have use in medical or veterinary application as implants or as inserts. The devices can be implanted surgically into the body or introduced into a body cavity of a human patient or an animal such that the active substance diffuses out of the device through hydrogel windows into the surrounding body region. The device may be in the form of a tube of water-permeable material having at least one port in the tube wall.
The above described systems and devices are intended to provide sustained release of drugs effective in treating patients at a desired local or systemic level for obtaining certain physiological or pharmacological effects. However, there are many disadvantages associated with their use. The need for a better release system is especially significant in the treatment of uveitis. Thus, there remains a long-felt need in the art for an improved device for providing sustained release of a drug to a patient to obtain a desired local or systemic physiological or pharmacological effect.